Mustapha Moshood K
Dept. of Zoology, University of Ilorin, Ilorin, Nigeria.
Rev Biol Trop. 2009 Sep;57(3):707-19. doi: 10.15517/rbt.v57i3.5486.
Agricultural and fisheries activities around the watershed of an African tropical reservoir (Oyun reservoir, Offa, Nigeria) were found to contribute significantly to water quality deterioration of the dam axis of the reservoir, leading to eutrophication of that part of the reservoir. This is evident from the high amount of nitrate (6.4 mg/l), phosphate (2.2 mg/l) and sulphate (16.9 mg/l) in the water body which was higher than most other reservoirs in Nigeria. These nutrients originate in fertilizer run-offs from nearby farmlands and were found in higher concentrations in the rainy season which is usually the peak of agricultural activities in the locality. The eutrophication was more pronounced on the dam axis because it is the point of greatest human contact where pressure and run-off of sediments were high. The eutrophication altered the food web cycle which consequently affected the fish species composition and abundance with the dominance of cichlids (planktivorous group) and decline of some species in the fish population. Best management practices (BMP) to control and reduce the eutrophication and improve water quality and fish assemblages should be adopted and adapted to suit the situation in the reservoir.
在非洲热带水库（尼日利亚奥法的奥云水库）集水区周边开展的农业和渔业活动，被发现对水库大坝轴线处的水质恶化有显著影响，导致该水库部分区域出现富营养化。这从水体中高含量的硝酸盐（6.4毫克/升）、磷酸盐（2.2毫克/升）和硫酸盐（16.9毫克/升）中可见一斑，这些含量高于尼日利亚的大多数其他水库。这些养分源自附近农田的肥料径流，且在雨季浓度更高，而雨季通常是当地农业活动的高峰期。大坝轴线上的富营养化更为明显，因为此处是人类接触最多的地方，沉积物的压力和径流都很大。富营养化改变了食物网循环，进而影响了鱼类物种组成和数量，其中丽鱼科鱼类（浮游生物食性群体）占主导，一些鱼类种群数量减少。应采用并调整最佳管理措施（BMP）来控制和减少富营养化，改善水质和鱼类群落，以适应水库的实际情况。
